(CNSNews.com) - Former New York Mayor Rudolph Giuliani endorsed Mitt Romney for president on Monday.
Giuliani, who had been leaning toward Newt Gingrich earlier in the season, says he believes Romney not only understands the economy -- but also "has the strength and toughness to handle foreign policy, which is an issue that hasn't been covered in this campaign."
Giuiani said foreign policy is his main concern, since the Republican candidates are "all pretty good on the economy."
"But I want to see somebody that really stands up for America," Giuliani told Fox & Friends. "I want to see somebody that can stand up to Iran and not write letters to the ayatollah, like Obama does. I think Obama has us down a very dangerous path with Iran, with this pathetic desire to want to negotiate with them. I think a ot of their decisions turn on that, and I don't think you're going to see that with a Mitt Romney."
Giuliani said Romney has proven he's "the most effective Republican" by winning the most primaries.
"I don't think the Democrats have any idea what they're running against. I mean Mitt Romney's a tough, tough campaigner. And his campaign organization is really tough. And if they think they're going to make this a campaign about Mitt Romney, I'm betting that his campaign is going to make it a campaign about President Obama -- which is, after all, what it is.
"This is the incumbent; the vote's going to be -- do we want four more yeas of this disaster? Or do we want to change it? And Mitt Romney is, you know, certainly a guy who can raise that issue I think very effectively."
Giuliani said he's "not on the list for running mate, I'm sure of that." But he said he will do whatever he can to help Romney win: "This country cannot stand four more years of Barack Obama -- and that's certainly true of the economy. I believe the untold story is -- it's even more true of foreign policy. He's got us going in exactly the wrong direction."